A service switching device of this generic type has a housing which comprises two housing halves and has connecting means for electrical connection to busbars and/or power lines.
Electrical service switching devices of this generic type are frequently in the form of mechanically acting circuit breakers which are used to disconnect electrical lines which are loaded with overcurrents at a high current level from the power supply system in the event of a fault. A fixed and a moving contact piece are normally provided for this purpose in an initial arcing chamber, and are connected to the respective connecting terminals. On opening of the switching contact, that is to say when the moving contact piece is lifted off the stationary contact piece, a switching arc is struck, and is quenched in an arc quenching device provided for this purpose. The arc that is struck commutates from the open contact pieces onto arc guide rails in order then to be split in an arc splitter stack, which is also referred to as an arc quenching chamber, where a high arc voltage is produced for current limiting, thus quenching the arc.
DE 102 42 310 A1 discloses an arc quenching arrangement for an electrical service switching device which comprises an arcing chamber (in which an arc is struck between a stationary and a moving contact piece during a switching operation) and an arc splitter stack which has a plurality of arc quenching plates, and into which the arc is guided via guide rails.
In order to increase the switching rating of service switching devices, various measures have been proposed in order to speed up the movement of the switching arc to the arc quenching device. Appliances whose switching rating has been increased in this way are also referred to as high-power switching devices.
DE 195 18 049 A1 discloses an electrical service switching device of this generic type having an initial arcing chamber and an arc quenching unit arranged adjacent to it. The quenching effect is assisted by an AC blowout device which uses an iron plate to produce a so-called magnetic blowout film which interacts magnetically with the arc in order to speed up its movement in the direction of the arc quenching unit. The iron plate can be arranged on one side of the chamber area of the initial arcing chamber.
In other service switching devices of this generic type, an AC blowout device is provided which comprises two iron plates adjacent to the initial chamber area in the lateral direction. The expression “iron plates” is used here in order to denote plates which have ferromagnetic characteristics. In addition to plates composed of iron, these may also be plates composed of some other ferromagnetic material, or plates composed of a composite material with a ferromagnetic component, or else plastic-extrusion-coated iron plates or plastic-extrusion-coated plates composed of another material with ferromagnetic characteristics.
The magnetic interaction which is used to assist the movement of the arc struck on contact opening in the direction of the arc quenching device in this case occurs only during AC operation, that is to say alternating-current operation. Service switching devices of this generic type are therefore also referred to as AC switching devices or AC high-power switching devices.
However, an arc also occurs during a switching operation in DC power supply systems or in direct-current operation, and should be quenched as quickly as possible in the arc quenching device. DC operation is subject to the additional difficulty that there is no zero crossing, and the movement of the arc into the arc quenching device should therefore be assisted by an externally generated magnetic blowout field. Corresponding appliances which are suitable for direct-current operation are also referred to in the following text as DC switching devices or DC high-power switching devices. DC switching devices are known from the prior art having permanent magnets whose magnetic field acts appropriately on the magnetic field formed by the arc, thus guiding the arc into the arc quenching unit.
With the exception of the blowout device, AC and DC switching devices are generally largely physically identical. However, since the permanent magnet for generation of the DC blowout field is fitted in the interior of the housing in known DC switching devices, a distinction must be drawn even at the start of the final assembly process for appliance manufacture between an AC appliance with iron plates and a DC appliance with a permanent magnet. Two separate production lines are even often provided, one to manufacture AC appliances and one to manufacture DC appliances.
DE 10 2005 007 282 A1 describes a service switching device in which there is no need to decide until a later time during final assembly whether the aim is to produce an AC or a DC appliance. Either iron plates to manufacture an AC appliance or permanent-magnet plates to manufacture a DC appliance are in this case inserted for this purpose into externally accessible recesses in the housing wall. However, even in this case, it is necessary to state from the start whether an appliance is intended to be an AC appliance or a DC appliance, and retrospective conversion from an AC appliance to a DC appliance is not possible.
Since the majority of the service switching devices of this generic type for which there is a demand in the market are AC appliances, but a manufacturer of service switching devices must be able to supply both AC and DC appliances, the provision of a separate production line for DC appliances represents a not inconsiderable cost factor.